Sealing of bridge expansion joint systems is important to protect the structural components below the joint. An elastomeric foam-type joint sealant has been developed for sealing small-movement bridge expansion joints. Laboratory tests including tension, compression, shear, bonding, stress relaxation, cure rate, tack-free time, and water tightness were performed on this sealant. In addition, loading-unloading behavior in tension and compression and effects of immersion in saturated saltwater solution on its engineering properties were investigated. The silicone foam sealant showed an increase in volume of ∼70 % on curing and attained approximately 80% of the 21-day curing strength in the first 7 days. Tack-free time for the foam sealant was below 1.5 h and comparable to that for the solid sealant. The mechanical test results indicated lower stiffness, greater extensibility, and better bonding associated with the foam sealant compared to the solid (unfoamed) sealant. The foam sealant exhibited smaller loss...

Dynamic loads crossing a bridge cause a structural response greater than if the same loads were static, a fact that has been known to structural engineers for over 125 years. This review paper presents a history of the evolution of railroad bridge impact formulas. Most non-North American countries operate passenger trains at much higher speeds than in North America. In the US, hundreds of very old open deck bridges will eventually likely be required to carry faster trains. This raises the question of what effects higher speeds will have on these bridges. What factors need to be considered in the upgrading of existing open deck bridges to accommodate newer and higher speed train equipment? A comparison of how dynamic impact factors are computed in countries around the world has been presented. Also examined are the differences and reasons between the impact requirements of North American railroads and European and Asian railroads.